Emergence and establishment of Staphylococcus haemolyticus ST29 in two neonatal intensive care units in Western...

Since 2021, several reports of Staphylococcus haemolyticus outbreaks in neonatal intensive care units (NICUs) have been reported in France. The aim of this study was to understand how S. haemolyticus became established in the NICUs of two facilities which share the care of newborns.

All positive S. haemolyticus clinical samples isolated between 2020 and 2023 and medical records were analysed. Phenotypic analyses consisted of typing using the quantitative antibiogram method and microbiological investigations using whole genome sequencing. Environmental samples and samples from the hands of healthcare workers (HCWs) were collected, with the same analyses undertaken if S. haemolyticus was identified. Observational studies of the hygiene practices of HCWs were also performed.

One hundred and sixteen neonates were positive for S. haemolyticus, of whom 44 (38%) were infected. The ST29 strain was highly predominant, and distinct clonal populations were identified. Transfers of newborns between the two centres, followed by cross-transmissions, could explain the dissemination of one population. Twenty-one environmental samples revealed the presence of the clones involved in neonates. One clonal population was also found on the hands of 15% of the HCWs sampled. Misconceptions about alcohol-based hand rub were observed, and daily disinfection of NICU equipment was not optimal.

Preliminary reports point to cross-transmission within and between the NICUs, either directly via the hands of HCWs or indirectly via contaminated environments, especially incubators. The ST29 lineage is identified in most NICUs, with the capacity to adapt locally and cause outbreaks.